Wireless brakes. Not a fan.

http://www.sciencedaily.com/releases/2012/02/120224110559.htm

Therefore, the Saarland computer scientist's mathematical methods should now verify the correct function and interaction of the components automatically. "The wireless bicycle brake gives us the necessary playground to optimize these methods for operation in much more complex systems," Hermanns adds. Therefore, his research group examines the brake prototype with algorithms that normally are used in control systems for aircraft or chemical factories. As a result, they found out that the brake works with 99.9999999999997 percent reliability. "This implies that out of a trillion braking attempts, we have three failures," Hermanns explains and concludes: "That is not perfect, but acceptable."

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D - there are also wireless bicycle brake-and-signal lights.
I'm not a fan. Here's why.
HACKERS.
Wireless means wireless hacking. I've picked up a 2600 mag in my time. Only that magnetic near-field tech that is being developed for secure financial transactions is tolerable.

Wireless brakes on a bike sounds like a good way to get killed.